Self-propelled machines are characterized generally as machines that include an on-board machine source of motive power and a mechanism coupled to the source of power for propelling the machine through and/or across a medium. For example, self-propelled machines may employ various different forms of machine power and appropriate mechanisms for propelling the machine across land, through the air, through or on top of the water, or even in outer space.
The movement of a self-propelled machine is controlled or guided by a guidance system that includes an operator and a guidance control system. The operator determines the guidance to be provided to the self-propelled machine. The guidance control system implements the guidance determined by the operator to guide the self-propelled machine by controlling, for example, the speed and direction of movement of the machine. The operator may be, in many cases, a human operator. A human operator may provide guidance to the guidance control system either directly, such as using a direct mechanical and/or electromechanical human interface to the guidance control system, or remotely, using a system to transmit guidance commands from a remote location to the guidance control system. In other cases, the operator may be a machine, such as an on-board or remote computer. In this latter case the self-propelled machine may be operated as an autonomous robot.
Examples of self-propelled machines include various self-propelled machines that are used by individual operators to perform yard work and the like. Self-propelled lawn mowers and snow throwers are examples of such machines. These machines typically include a motor, such as an electric motor or gasoline or diesel engine, which is used to drive wheels that propel the machine across the ground. The same motor that powers the drive wheels typically also is used to power a task payload of the machine. For example, the task payload of a self-propelled lawn mower may include a mower blade driven by the machine motor. The task payload of a snow thrower may include an auger and impeller driven by the machine motor.
The operator of a typical self-propelled lawn mower or snow throwers is a human person who walks behind the self-propelled machine to guide it. In the most basic scenario, the guidance system for such a machine includes a lever or some other mechanism for controlling the speed of the machine and a handle for directing the machine in the desired direction. The speed control mechanism may provide for the operator to select from between just two speeds, forward and stopped, or may allow the operator to stop and start motion of the machine and to select from among multiple forward and reverse speeds. The operator may guide the direction of movement of the machine by pushing and pulling on the handle to force the machine to move in the desired direction.
Some self-propelled lawn mowers and snow throwers provide a mechanism to assist the walk behind human operator of the machine to turn the machine in a desired direction. For example, such a mechanism may include levers on the right and left sides of the machine handle that are actuated by the human operator. These levers are coupled to the wheel drive mechanisms of wheels on the right and left sides of the machine, respectively, such that drive power to the corresponding wheels is removed when the corresponding lever is actuated. Thus, for example, to turn the machine to the right, with the machine moving forward, the operator can actuate the lever on the right side of the machine handle. This will remove drive power to the right side drive wheel of the machine, causing it to stop. The left side drive wheel is still being driven, however, moving the left side of the machine forward, thereby turning the machine to the right as long as the right lever is actuated. The machine may be turned to the left by actuating the left side lever in a similar manner. If both levers are actuated simultaneously, drive power is removed from both the right and left side drive wheels, thereby bringing the machine to a stop.